[Role of Ca-calmodulin- and cAMP-dependent reactions in forming the cardiac cycle]

The mechanisms of regulation of calcium ion concentration in the heart muscle during cardiac cycle have been considered. A great deal of attention has been devoted to the interaction of Ca2+-calmodulin- and cAMP-dependent reactions in the heart contraction-relaxation processes. The hypothesis on the two-phase structure of cardiac cycle has been proposed. This hypothesis allows to explain some biochemical mechanisms in the positive inotropic effect of catecholamines, cardiac glycosides and caffeine.